Here's my problem with this "update every 2-3 years" idea; I don't want games in 2020 and 2021 to run like shit on my base Switch. I paid $479 for my system, I expect at least a good 5 years of support from it without being forced to buy gimped, choppy versions of games that come out after the Switch 1.5, fuck that shit.
I'd think if Nintendo did a 3-year upgrade formula, they'd require 1st and 2nd party devs to use the base Switch as the lead platform and go from there. The big bonus would be in performance updates for existing games like BotW and Xenoblade 2 as well as the acquisition of 3rd party games that otherwise would not be able to hit the OG Switch. That is, assuming that they use the upcoming Xavier SoC for a hypothetical Switch 2.